A known slide gate valve (hereinafter referred to as "SV" equipment) consists of a plurality of plate bricks, a housing arranged at the bottom surface of a vessel for molten metal, said housing storing said plate bricks, a surface pressure load mechanism for supporting suitable surface pressure between the contact surfaces of said plate bricks, and a slide plate driving mechanism.
A group of plate bricks are replaced by new ones when they have reached their life end. At that time, the replacement working is carried out in such a manner that the SV equipment is opened under on-line system, the plate bricks are removed one by one whereafter new plate bricks are set one by one, and the surface pressure is loaded by a surface pressure load mechanism thereby to complete the replacement. Another method for the replacement is such that the SV equipment is removed and a new SV equipment incorporated with new plate bricks is substituted therefor. In such method, the replacement working is carried out by an exlusive use machine, and the removed SV equipment is sent to the maintenance section (off-line) for repairing.
Said plate bricks are in one body, the periphery of a refractory provided at their center with a molten steel flow opening, is clamped by an iron band or wire, and the plate bricks are delivered in a single unit to customers. Further, to avoid leakage of molten steel and involvement of external air into the molten steel, the plate bricks conventionally are made large-sized.
Thus, the known plate bricks have the following demerits.
(1) Since the plate brick replacement working effected under on-line system after casting is carried out 20-30 minutes after casting, the temperature of the SV equipment and the refractory remains considerably high, and since it takes about 15 minutes for such working the working is a heavy hot working. Further, being a heavy hot working, it is likely that the working itself becomes moderate thereby causing troubles such as molten steel leakage due to erroneous setting of the bricks. Additionally, setting of the refractory bricks one by one makes mechanization difficult. PA1 (2) Even in the case of replacing the refractory bricks in maintenance section (off-line) the bricks need to be replaced before the temperature of the SV equipment and the refractory is lowered to room temperature. Even in this stage the operation condition is still under a heavy hot working. Even in the case of replacing the refractory bricks after the temperature has lowered to room temperature, the weight of a single refractory is 5-25 kg, and therefore the heavy hot working still remains. PA1 (3) Plate bricks are constituted mostly by refractory, it is difficult to process refractory, great cracks are likely to generate in the processed portions, and therefore it is scarcely possible to mount a temperature sensor. PA1 (4) Since an iron band or the like is shrink fitted or overlap wound, for clamping, to the periphery of a plate brick, the plate brick cannot be split in type. That is, in the case of plate bricks in one body structure, cracking is apt to occur, even the positions of generating cracks are irregular thereby to cause an abnormal melt-down, and this causes troubles or shortens the life of the bricks. PA1 (5) In the known methods the cooling effect of the plate bricks was not sufficient. It was all to air cool the interior of the SV equipment so that sufficient cooling was not effected, the clamping effect of said iron band is lost due to high temperature, and the SV equipment in entirety is promoted for deformation. PA1 (6) A lot of labor and working time are required in that the plate bricks are discharged one by one depending on their kind, and new ones are set also one by one to the SV equipment. PA1 (7) Erroneous setting of the plate bricks is likely to occur so that it is difficult to adjust the plate bricks themselves. PA1 (1) For joining with the insert nozzle (pouring-out nozzle 5) there is required, causing complication, a mechanism for moving and pressing said cassette in the rectangular direction to the shell of a tundish (TD). PA1 (2) Coupling with a driving mechanism (oil pressure cylinder) for sliding is required, said driving mechanism is mounted in the insertion position of the cassette so that after the cassette insertion it is necessary to separately mount another driving mechanism to the tundish or ladle shell, and coupling working with the cassette is also required. Thus, the known techniques are not practical. PA1 (3) Because of the coupling with the insert nozzle the shape of the cassette must be tapered as shown in FIG. 15 of Publication No. 59-21701. Such shaping makes the space between the ladle or the tundish shell and the cassette 42 wide, the insert nozzle 5 and the cassette 42, including the connection portion therebetween, appear naked, and cracking is apt to occur thereby to cause troubles such as leakage of molten steel. PA1 (4) In case a cassette is inserted in the combination of the plate bricks illustrated in FIG. 1 of said publication, the known technique is not practical in that the bricks are not fixed to the sliding and that the bricks are not connected to the driving mechanism for sliding. PA1 (5) As shown in FIGS. 3 to 5, the surface pressure is loaded with a force for insertion in the horizontal direction, so that the insertion needs to be made with rather a great force. This requires an insertion device therefor, and therefore the known technique is not practical in relation to the driving mechanism for sliding.
Referring to the working environment, since the slide gate valve is cleaned after the removal of the refractories after use, air blows or the like create a powdery dust atmosphere. In such case, a merit is just for mechanization of hot working, and not only a great amount of cost incurs for mechanization but also the refractory replacement working must be carried out by a worker so that man power cannot be saved.
To solve the above problems of known systems, a technique for cassettizing the respective plate bricks is disclosed in Japanese Patent Publication No. 59-21701, and a method for surface pressure loading in the case of using a cassettized plate brick assembly is disclosed in Japanese Patent Publication No. 60-15429.
However, even the known techniques described in said publications have the undermentioned problems because a cassette is inserted in parallel with the sliding surfaces.
On the other hand, since tapering is in the insertion direction the positioning (circumferential direction to the nozzle core) of the insert nozzle 5 is difficult, and if the joints are not secured it is likely to cause troubles such as leakage of molten steel.